This invention relates to polyimides which are prepared from dioxydiphthalic anhydrides. Polyimides are used for various purposes including films, coatings, and molded articles. As a class, the polyimides are characterized by excellent physical properties, such as heat resistance, high impact strength and wear resistance, and the like. They generally exhibit good chemical resistance to a wide range of solvents Their excellent retention of mechanical and other physical properties at high temperatures is attributable, at least in part, to the fused-ring nature of the aromatic monomers from which the polymers are formed. The properties of polyimides can be varied depending on the specific selection of dianhydrides and diamines employed. It will be generally appreciated by those skilled in the art that a need exists for a broader selection of polyimides based on the various properties needed for applications in the electrical, electronics, automotive, aerospace, and packaging industries The polyimides of this invention are based on the use of a novel dianhydride reactant, dioxydiphthalic anhydride, optionally in combination with an oxydiphthalic anhydride.
The preparation of oxydiphthalic anhydride and its use in the preparation of polyimides is known. Various methods for the preparation of oxydiphthalic anhydrides have been described in the chemical literature. Such a method, shown to be useful in the preparation of oxydiphthalic acids and anhydrides, involves the oxidation of tetramethyl diphenyl ethers. See Kolesnikov, G. S. et al Vysokomol. Soyed, A9, 612-18 (1967); Marvel, C. S. et al, J. Am. Chem. Soc., 80, 1197 (1958); and Latrova, Z. N. et al, Volokna Sin. Polim., 15-24 (1970).
Three Japanese patents to Mitsui describe preparations based on reactions of substituted phthalic anhydrides. Japanese Patent Document 80/136, 246 (Chem. Abst. 95:42680) teaches the coupling of 4-nitrophthalic anhydride in the presence of sodium nitrite to form oxy-diphthalic anhydride. In Japanese Patent Document 80/122, 738 (Chem. Abst. 94..83799) Mitsui disclose the reaction of 4-halophthalic acid or anhydride with a base to yield oxydiphthalic anhydride. In Japanese Patent Document 80/127, 343 (Chem. Abstr. 94:191942) the reaction of 4-halophthalic anhydride, Na.sub.2 CO.sub.3 and NaNO.sub.2 in dimethyl sulfoxide to form 4,4'-dihydroxydiphthalylic phthalylic anhydride is described.
German Patent No. 2,416,594 (1975) discloses the coupling of 3-nitrophthalic anhydride in the presence of metal nitrites, such as sodium nitrite to form oxydiphthalic anhydride.
Markezich, R. L. and Zamek, O.S., J. Org. Chem., 42, 3431 (1977) describe reaction of 4-nitrophthalimide with potassium fluoride in dimethylsulfoxide to form the corresponding oxydiphthalimide which may be converted by hydrolysis to form the acid and ring closure to form the dianhydride.
U.S. Pat. No. 4,697,023 to Schwartz and Pawlak, discloses the preparation of oxydiphthalic anhydrides by reacting a halophthalic anhydride with water and an alkali metal compound such as KF, CsF, or K.sub.2 CO.sub.3 in the presence of a polar aprotic solvent.
U.S. Pat. No. 4,794,157 to Berdahl and Nye discloses polyimides prepared by the intercondensation of an aryldiamine with a mixture of oxy-diphthalic anhydride and an aromatic bis(ether anhydride), such as 2,2-bis[4-(3,4-dicarboxyphenoxy)-phenyl]propane dianhydride. The polyimides prepared are described as tough flexible transparent copolymers having Tg's from about 217.degree. C. to 300.degree. C.